Ventilation systems for buildings use fans and blowers to move air from the building when needed. The fans or blowers must move thousands of cubic feet of air in an efficient, quiet manner. Typical types of fans are centrifugal fans and axial fans.
Centrifugal wheels are well known in the art and have a circular front plate and a back plate with a series of blades extending between the two plates. Air enters the centrifugal wheel through the front plate and is moved radially outwardly due to the rotation of the blades. Conventional centrifugal wheels have front plates and back plates with the same diameter, giving the wheel a cylindrical shape.
When centrifugal blowers, or wheels, are used in axial fans, the wheel moves the air radially outwardly. A problem arises when the wheel is in close proximity to the housing. This problem is addressed in U.S. Pat. No. 5,810,557 (Akinkuotu) and is illustrated in FIG. 1 of that patent. Akinkuotu addresses this problem by using fan blades that are angled relative to the longitudinal axis of the wheel. This results in the air moving in a radial and axial direction, as shown in FIGS. 5 and 7.
U.S. Pat. No. 5,171,128, to Williamson et al., discloses a wheel with cut outs 80 formed in the back plate and between the blades. This gives the back plate a saw tooth appearance, as seen in FIG. 3. U.S. Pat. No. 6,042,335, to Amr, discloses a centrifugal wheel with a hub 15 and blades 13 extending beyond the edge of the hub as best seen in FIG. 1.
It is an object of the invention to provide a centrifugal wheel having a frustoconical shape.
It is another object of the invention to provide a centrifugal wheel having a front plate with a greater diameter than the back plate.
It is another object of the invention to provide a centrifugal wheel which efficiently moves air.
It is yet another object of the invention to provide a centrifugal wheel used in a ventilation stack to move large amounts of air from a building.
These and other objects of the invention would be apparent to one of ordinary skill in the art after reading the disclosure of the invention.